This invention relates to the field of radiation-curable gels useful for cosmetic adornment of natural nails, artificial fingernails, toenails and artificial nail extensions.
The use of radiation-curable gels in formation of nail enhancements or artificial nails has been an important part of the cosmetic industry since it was first introduced. U.S. Pat. No. 4,682,612, describing the use of actinic radiation-curable compositions suitable for preparation of artificial nails, is representative of this technology.
Ultra-violet radiation (UV) is the most conventional form of radiation used to cure gels in this art, however, visible light curing systems are also known. UV-curable gels are most typically applied by professional nail technicians. Such UV-curable gels are usually composed of acrylic or methacrylic monomers and oligomers in a gel-like state that requires curing under a UV lamp. Such nail finishes can be applied directly to natural fingernails or toenails, or alternatively can be applied to nail extensions bonded to fingernails. In many cases, the artificial nails are coated with conventional nail polish after they are cured.
In order to avoid the need to coat the artificial nails or natural nails with conventional nail polish, in more recent years, the preparation of gels containing colorants, particularly pigments, has become known in this art. However, the previously suggested processes used to prepare such colored gels have several disadvantages. One such process, the direct of addition of pigment powders, is described in US Pat. Pubs. US2006/0283720 and US2010/0008876. The direct use of pigment powders brings with it the disadvantages of difficulty in handling, inconsistent dispersion leading to poor color control, the need for high shear mixing or milling full batches of material, and the need for expensive large scale equipment. The direct mixing of all components including pigment powders in a suitable solvent is described in U.S. Pat. No. 5,985,951 which brings the same disadvantages. As an alternative to incorporating pigments per se, a gel composition combined with commercial nail polish is described in U.S. Pat. No. 6,803,394. In this patent, commercial nail polish is added to a UV-curable artificial nail gel by the applicator as a means for coloring the gel and resultant artificial nails.
The use of commercial nail polish is undesirable in that it limits the depth of color that can be achieved in a given coating weight. Thus, compared to the commercial nail polish itself, a lower color density will be achieved and attempts to increase the amount of nail polish will lead to systems which give poor curing characteristics or discomfort due to the thick coating required to provide the desired color depth.
It has been a long felt need in this art to provide integrally colored artificial nails which have a reproducible, predictable color when cured.
There is also a need for an improved method to produce color containing UV-curable gels which give high color density.
There is also a need for an alternative to directly adding pigments to artificial nail gels to avoid the requirement of applying high shear to the gels in order to effectively incorporate the pigments.